[RFI] Switch mode lamp noise

At 09:32 PM 2/6/03 +0700, msole wrote:
>When we moved into our house I had some nice halogen spot lamps fitted
>in the shack. Didn't realise at the time that these things have a
>switching supply to produce the 12 volts for the bulb. With only a
>single one fitted to the track it produces enough rubbish to wipe out
>everything from top band through ten. Antennas are outside 100 foot away
>fed with coax.
>>They are a very simple design, recified household supply powers an
>oscillator which is then transformed down to 12 volts. Scope shows a
>nice 11KHz sqare wave. These things are two wire only, no ground.
>>Is there anything I can do to get rid of the noise, short of either
>replacing them or fitting a 20 amp DC supply in the attic?
This may not be relevant, but the 12V halogens in my kitchen are from GE,
probably use the samne type of voltage conversion, and they are dead
quiet. This suggests to me that routine RFI treatment may do the trick --
RF chokes and bypass capacitors, maybe an AC line filter.
73, Pete N4ZR
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